The Harmful Side Effect of Cleaning Up the Ocean

Egger stresses that TOC wants to make sure its plastic-cleaning efforts are helping marine life, not harming it. But it’s more complicated than simply trying to minimize the amount of marine life taken out of the ocean along with plastic, he says. If crustaceans or sea anemones from other regions cling to plastic debris and hitch a ride to the middle of the Pacific Ocean, they could feed on neuston there. Is it then right or wrong to remove these invaders, who may be disrupting the local ecosystem? “There is always marine life associated with the plastic,” says Egger. “But very often, it’s marine life that does not belong there, because the plastic does not belong there.”

A study published in mid-April offers some clues as to which traveling species could pose a problem. Researchers at the Smithsonian Environmental Research Center examined 105 pieces of plastic debris they had obtained in frozen form from TOC. They found traces of species normally found in coastal waters that had used floating plastic as rafts and ended up in the Great Pacific Garbage Patch—in particular nets, ropes, buoys, boxes, and cylindrical eel traps from the fishing industry. Some species also appeared to reproduce in their new offshore home. For example, some shrimp-like amphipods were carrying eggs in their brood pouches.

This isn’t surprising, says Martin Thiel, a professor of marine biology at the Catholic University of the North in Chile. Marine organisms have been found colonizing all sorts of floating materials in the ocean, including volcanic pumice, seaweeds, and wood, at least until these items start to degrade and sink. Whether it’s organisms that settle on more durable plastic debris or that float at the surface next to it, Thiel says that they can’t simply be separated from plastic. “What’s out there, we better leave it in peace, because by removing it, we may do more harm,” he says.

Lanna Cheng, professor emerita at the University of California, San Diego, is somewhat less concerned. Sometimes neuston are floating among plastic, sometimes not. Some neuston are able to swim up and down. And storms can come along and mix things up. Because neuston aggregations appear to be so patchy, accidental catches would likely not significantly affect their populations, she says. And because TOC invests so much time and resources in offshore trips, she welcomes the organization’s contribution to science by offering marine biologists like her opportunities to collect samples. “The surface community [of marine life] is a community that was hardly studied until plastic pollution became a problem. Part of the reason was that there was very little economic value,” she says. Cheng herself has spent her career studying insects that have evolved to literally walk on the open ocean and survive.

Helm, however, remains critical, in part because she believes that studies should first show that there is no impact on neuston, before cleanups are carried out. “If they really do the work and demonstrate that their efforts have no impact on ocean surface life, then I will be excited to see that they took the criticism and made changes,” she says. One change crucial to neustonic species was made recently. In May 2023, TOC more than doubled the length of its net barrier, which now extends to 1,750 meters. As part of the upgrade, the mesh size of the nets in the retention zone, where plastic is held before being hoisted onto the ships, has been increased from 10 to 50 millimeters square. This should allow very small creatures like blue buttons and violet snails to pass through the nets, but by-the-wind sailors, for example, can grow larger than this. However, increase the mesh size any more than this, and pieces of debris could start to seep through.

The two sky-blue ships are currently cruising across the Great Pacific Garbage Patch again, testing the updated barrier in the hope that they can collect more plastic per trip. Ridding the open ocean of plastic remains a Sisyphean task. As more plastic enters the patch, and scientists learn more about the creatures living there, TOC still has many obstacles to overcome before it can scale up its operations. “Our purpose is to help those organisms out there, but you need to make sure that the way you help is actually helping them,” says Egger. “And that's what we're trying to figure out.”